The instant invention relates to a method of manufacturing iron garnet layers on a substrate, in a layer sequence of different order by means of RF-cathode sputtering in an inert gas plasma, making use of a target which comprises predominantly an iron garnet phase in addition to residual phases having an almost equal sputtering rate, the ions of said inert gas plasma bombarding the growing layer having an ion energy of less than 10.sup.2 eV and a pressure in the range from 0.1 to 2.0 Pa.
Such a method is known from German Patent Application P 37 04 378.1. Layers which are manufactured according to this known method are used to form optical waveguides for non-reciprocal optical components. In the case of reversible magnetooptical data storage in iron garnet layers or orthoferrite layers or hexaferrite layers, morphologically "smooth" layers are very advantageous to attain a low noise level in the read signal or in the case of optical waveguides to keep the scattering losses at a low level.
For example, when polycrystalline iron garnet layers are deposited on substrates of a different order, layers having a certain surface roughness are obtained, i.e., which are not morphologically "smooth". For example, if iron garnet is deposited on glass substrates in a polycrystalline form by means of RF-cathode sputtering in an argon plasma at a pressure of 0.6 Pa and temperatures exceeding 520.degree. C., a sequence of coarse, fine and, finally, columnar crystallites having a static crystal orientation is obtained, which leads to layers having a relatively large surface roughness. The serrated magnetic domain structure with a high coercive field strength and relatively high light-scattering losses, which are the concomitants of this morphology, denote a distinct grain structure.
It is an object of the invention to provide a method by means of which polycrystalline iron garnet layers can be manufactured, the morphology of which approaches that of monocrystalline iron garnet layers, and which iron garnet layers have a distinct texture.